1. Field of the Invention
The present invention relates to a powertrain member, more specifically, to a powertrain member mounted on a vehicle.
2. Description of the Background Art
A conventional powertrain member is disclosed in, for example, Japanese Utility Model Laying-Open No. 01-174505.
Japanese Utility Model Laying-Open No. 01-174505 discloses that, in a conventional powertrain member such as a gear, a through hole is provided in a disk portion for reducing a weight and a noise. When a through hole is provided in a powertrain member such as a transmission of an automobile which transmits relatively large mechanical power, though concentration of a stress around the through hole becomes a concern, the through hole may be provided before heat treatment. In this situation, an effect of heat distortion is increased. On the other hand, laser processing is preferably used to provide the through hole because the processing can be performed relatively readily. When a through hole is formed before heat treatment to such an extent that the effect of heat distortion can be ignored and then a desired through hole is formed after heat treatment by laser processing, however, the processing becomes difficult if the through hole is chamfered because a laser is reflected in a chamfer portion.